Note: I got some comments that parts of the
information on this page regarding the exact evolutionary process of
sight isn't scientifically (genetically) correct. This surely is true and I have to do some
more research in this field, but "alignment" played a big role in the processes that created "convergent evolution". So at this moment, this page
can be seen more as a bundle of rough ideas that you can reflect up on.
And If you like to be noticed when I've updated this page, you can add me
as a twitter-friend (see bottom of the page for my address).

Evolution adapted the eyes of different species to different types of environments. There are Nocturnal, Diurnal and arrhythmic types and each section has their predators and prey animals. First we take a look at the size of the Lens of the different species.

Nocturnal animals have big lenses and a small Vitreous Humor. Their eyes work as a sensor for movement in the dark and mainly use Rod type cells (see: 2.1 The Retina: Rods and Cones ) for night vision. The big lens also converges more light and gives a brighter image.

Diurnal animals have small lenses and a big Vitreous Humor. The small lens gives more depth of focus and focus becomes less critical (see: 1.6 Size & Curvature ). For human, the lens also clearly projects what's right in front of the view-line on to the Cone-type cells of the Retina, sensing color information and high acuity.

Arrhythmic animals have medium lenses and a medium Vitreous Humor. This gives a mix of the above type of animals providing them the ability to live during the day or to roam during the night.

Second are the pupils, they work as the Primary-Masking-Alpha-Areas of the eyes, and contract when light is increased or when more focus is needed,
in contrast to Alpha-Areas that surround the eyes although the eyebrows can
be frowned and eyelids can be narrowed to increase Alpha.

Conclusion: Cats who live close to the ground have to keep track of horizontal, back and forth moving objects like mice, a vertical alignment improves this ability, so they narrow their pupils into a vertical-shape (see topic: 1.5 Alignment). Horses who have a higher perspective and live originally in open fields with horizons need to have a vision for eating grass, they already have a big nasal-intersection so they narrow their pupils in a horizontal-shape, they haven't got the natural ability to stay focused on a target like preditors. Owls have a fine balanced visual system with the characteristics of humans, the narrow their eyes likewise, to a smaller circle. Although they are predators of the night they can catch mice thanks to their oblique Nasal-Masking-Alpha-Area, almost the same as cats have.

Below are some more samples of different animals and their typical shaped pupils.

A1: It is not so much my theory it is a physiological principle, that I experienced by changing the masking of my eyes. This gave me the opportunity to understand some of the basic mechanics of our sight, and how it's applicable for nearly every organism. Masking helps us to align and stay in balance, to move and see in a particular way, to observe, track prayâ¦

It's like the moon when it is closely to the ground it looks bigger, because the relation between a steady object (earth/us) and the a free object is shorter and thus more stable. Also the framing is different when the elements are closer in 'play'. The earth and the buildings are masking elements who give us alignment to rest our sight upon.

In our early development stages we had to move our whole body to look around to catch pray like crocodiles, fishâ¦. The more we could detach the action of looking around from moving our body the more freely our brain has developed, but the basic principles of alignment are still there.

We look around, not only by eye-rotation but by refined body movement, bending of knees, hips, upper-body, shoulders, neck, this gives us almost unlimited freedom to look around and align ourselves to our environment. And over time it has given us the impression that we only look by moving our eyes.

Q2: Why do you think "Masking helps us to align and stay in balance, to move and see in a particular way, to observe, track prayâ¦"?

The implication seems to be that someone seeing less of their environment (because of masking) is likely to be at an advantage. I suspect that our retinas and brains do what you call the "masking" when we point our yellow spot at whatever attracts our interest. Anything outside of the yellow spot isn't literally masked, but is not paid as much attention to, unless there is movement there. (We have good motion sensing in the peripheral field.)

A2: Being at an advantage is very relative, â¦ and the masking is needed for focusing, align, so one has more grip on the target, for a cow this is grass, for an eagle it could be a rabbitâ¦

So when we look we rest our sight and don't realy focus, but for tracking we have to aim, and use masking elements, look at how archers aim (pix below) and how an eagle is build to have maximum alignment not necessarily to reduce peripheral sight â¦ look also how archers ad tools to keep their bow balanced in the same way nature has provided us with similar tools.

When we read we constantly slightly move our head/body and align relatively to the masking we haveâ¦

Q3: The pupil is completely out of focus at the retina, and (b), the retina, which is in the focal plane, has a structure, such that the central region is filled with cone cells onyly, and is the area used for concerntrated study of the field of view. The peripheral has a mixture of cones and rods, and is more useful for detecting movements outside of the area of great interest. Such movements could represent a danger, but the eye/brain system does not want to be distracted by details there, unless they make a sudden movement (potential threat). Anyway, I think that the edge of the yellow spot is therefore the real "ask". It is well defined - there is a vein running round that edge, over the retina, but no veins within it (the cones within rely on the pigment epithelium for their blood supply).

A3: You are right that the transition area from Foveal (yellow spot) to peripheral provides us with a marker. But if you look at the development of our sight you'll see that there are also other elements that are important.

Light is a basic material and it behaves in a logic way. Its a bundle of energy vibrations and depending on the material it's reflected by, it lose energy and gets a different frequency: color, tint. Where it's blocked there's a shadow.

The first (light) sensitive cells could only detect difference in temperature: light or not (0/1). When something passed by these cells, organisms received a potential.

Over time our eyes became more refined, and most trackable movement came from the side or moved to the side. There where no organism that moved straight towards us, and we couldn't move straight towards them, because we all didn't have the proper alignment tools yet. Unless you where a plant focusing on one energy source such as light and locking yourself to one place.

Thus the central area (fovea) became a new contrast point vs peripheral (0/1) and it developed itself for detecting subtle variations of light (colors). The peripheral area started to interact with masking elements to refine it's view. Our visual system developed also in such a way that the foveal area stayed out of reach of the facial masking elements, because it would disturb this part of our view.

Foveal cones are fine sensors and we need to turn our eyes to focus and sense edges, by moving our eyes in a saccadic way, we interlinking our foveal view with our peripheral view. To get overall grip we use our wider peripheral view along with masking alignment elements as a reference to rest our view upon and/or to guide our short saccadic tracking fluently.

Referring back to 'The Archers' they coordinate the different visual elements such as alignment, finding balance for their body position, with the refined saccadic movement to find the find the right 'moment' to shoot. Same thing for the eagle, he uses his beak to position himself and uses saccadic eye-movement to adjust. Note our peripheral view has two marker edges and one is shared with the foveal area.